1. Field of the Invention
The present invention relates to a continuous testing device for a water pipe, particularly to a continuous testing device for detecting volume changes due to axial pressure.
2. Description of Related Art
For manufacturing of flexible pipes, appropriate material for practical use needs to be employed. Testing of material samples is performed to ensure that requirements are met.
Flexible pipes are produced in various sizes, having inner diameters of up to 4000 mm. With water pressure in practice reaching 20 kg/cm2, axial forces on water pipes are as large as thousands of tons, and large mechanisms (usually oil pressure cylinders) are required to overcome axial pressure. Testing of flexible pipes for expansion, deflection and eccentricity under pressure is fraught with difficulties, since high water pressure readily leads to changes of length and volume. Due to the incompressibility of liquid, a small volume change immediately leads to a large pressure change, and a stable condition cannot be achieved. Therefore, if there is no way to release or refill water, testing data of flexible pipes will turn out to be faulty, and the testing process will have to be stopped.
A conventional testing device for a flexible pipe used in manufacturing plants, as shown in FIG. 2, comprises: a frame 100, carrying mechanical weight; a fixed plate 101; a movable plate 102, two joints 106; two horizontal oil pressure cylinders 104; and a vertical oil pressure cylinder 105. The fixed plate 101 is mounted on one end of the frame 100, providing a fixed base for testing shifts of a flexible pipe section 107, and has two canals leading to the flexible pipe section 107 to which an inlet 101a and an outlet 101b are respectively connected for applying pressure. The two horizontal joints 106 are connected with an upper end and a lower end of the fixed plate 101, respectively, having far ends connected with the movable plate 102, with threaded bolts 103 passing through the movable plate 102 serving to adjust holding forces. The two horizontal oil pressure cylinders 104 are connected with the upper and lower ends of the fixed end plate 101, respectively, exerting horizontal force on the movable plate 102. The vertical oil pressure cylinder 105 is set on a movable base 108 on the frame 100, applying vertical force on the movable plate 102.
During testing, the flexible pipe section 107 needs to withstand a large axial force. For the joints 106 and threaded bolts 103 carrying the axial load, water is let out of the flexible pipe and nuts 103a on the adjusting threaded bolts 103 are turned by a preset degree. Then water is through the inlet 101a filled into the flexible pipe. During filling, changes of length and shifting of the flexible pipe section 107 are sensed. However, since the nuts 103a on the threaded bolts 103 determine a fixed state, there is no way continually to monitor shifting of the tested pipe section 107. Thus several measurements require repeated adjusting of the nuts 103a on the threaded bolts 103, which is not a realistic test of the tested pipe section 107. In real use, the tested pipe section 107 undergoes continuous change of pressure. Therefore, conventional testing does not reveal real properties of the tested pipe section 107.
Above explanation shows that a conventional testing device for a water pipe has the following shortcomings:
1. Only discontinuous, static monitoring is possible, no continuous changes of pressure are simulated.
2. Testing in several steps is time-consuming and cumbersome.
3. Test data do not correspond to the behavior of the tested pipe and are imprecise, not providing a solid base for judging the properties of tested pipes.
4. Tests have a high rate of failure, wasting cost and effort.
It is the main object of the present invention to provide a continuous testing device for a water pipe allowing safe testing at low cost.
Another object of the present invention is to provide a continuous testing device for a water pipe for precise testing with reliable data.